1. Field of Invention
The present invention relates to the medical uses of ultraviolet light.
2. Description of Related Art
There is well-documented evidence that blood pressure tends to be lower in the summer than winter and higher as one moves farther from the equator. Previous published studies have attributed these findings to the increased vitamin D levels associated with sun exposure.
Based on our experiments we have found that there is an immediate (within minutes) fall in systolic blood pressure in both black- and white-skinned individuals and in both normotensive and hypertensive subjects who were exposed to measured, modest doses of artificially produced sunlight wavelengths. The ultraviolet light to be used in this invention is preferably UV-A light having wavelengths of 315-400 nm, more preferably 320-400 nm.
Such an effect could not be attributed to the production of vitamin D, which must go through several metabolic steps in the skin, liver and kidney to become active.
A more likely explanation of what we observed is a result of the almost immediate effect of nitric oxide (NO) in dilating blood vessels. There are two mechanisms described by which NO is released in blood vessels. One is the induction of NO formation by the enzyme called iNOS. The other is the release of preformed NO precursors when stimulated by near-visible ultraviolet light in a process called “photorelaxation”. The familiar sunburn reaction has been shown to be mediated by an iNOS effect. Thus there are adequate explanations for the immediate blood pressure lowering effect we saw when our subjects were exposed to physiologic amounts of artificial sunlight.
We also believe there to be a systemic effect from NO released in the skin. One treatment for coronary artery disease-caused chest pain (angina pectoris) is to apply nitroglycerin ointment to the chest wall over the heart. The nitroglycerin ointment releases NO through the skin and it has an effect on the heart.
NO is a profound promoter of increased blood flow. It also has been described as having anti-carcinogenic, anti-inflammatory and anti-arteriosclerotic effects by way of its chemical action of neutralizing oxygen-free radicals.